1. Field of the Invention
The present invention relates to a method of manufacturing a cathode-ray tube and, more particularly, to a method of forming a film having anti-reflecting and antistatic properties on the outer surface of a cathode-ray tube faceplate.
2. Description of the Prior Art
Various non-glare treatments are commonly used to decrease reflection of external light on the outer surface of a cathode-ray tube faceplate, thereby to diminish the adverse effects of the reflected light. In one of these non-glare treatments, an alcohol solution consisting of alcoholate of Si, Si(OR).sub.4 is spray-coated on the outer surface of the faceplate, thereby forming numerous fine projections thereon.
Japanese Patent Disclosure (Kokai) No. 61-118932 discloses a practical non-glare treatment in which the film formed by the spray-coating of an alcohol solution of Si(OR).sub.4 on the outer surface of a faceplate is sintered at 150.degree. C. or less, thereby to endow the film with antistatic properties. Since the sintering temperature is relatively low, the adherence of the film to the faceplate may be reduced. To prevent this reduction of adherence, NHO.sub.3 is added to the alcohol solution. The above non-glare treatment, in which the film is formed of an alcohol solution of Si(OR).sub.4, takes place in the manner shown below.
(1) Hydrolysis (generation of a silanol group) EQU .tbd.Si-OR+H.sub.2 O.fwdarw..tbd.Si-OH+ROH
(2) Condensation of a silanol group (generation of a siloxane bond) EQU .tbd.Si-OH+RO-Si.tbd..fwdarw..tbd.Si-O-Si.tbd.+ROH EQU .tbd.Si-OH+HO-Si.tbd..fwdarw..tbd.Si-O-Si.tbd.+H.sub.2 O
In the above reaction, the silanol group gives an antistatic effect to the film, and siloxane bond serves to increase the adhesion of the film to the faceplate. Reaction (2) is promoted when the film is heated.
As long as the film is moderately heated, the silanol group remains in the film, whereby the film is sufficiently antistatic. In this case, however, the adherence of the film to the faceplate is insufficient since the siloxane bonds in the film is small in number. On the other hand, when the film is overheated, it cannot be adequately antistatic. Although acid such as HNO.sub.3 can promote reaction (1), thereby reducing the time required for the aging of the coated film, it cannot serve to increase the adherence of the film sufficiently.